The present invention relates to a device for detecting a filling density of filler in a rod-shaped article and, more specifically, to a detecting device suitable for detecting a shred tobacco filling density in a tobacco rod produced by a cigarette manufacturing machine.
This kind of filling density detecting device conventionally uses radial rays. More specifically, the detecting device emits radial rays toward a tobacco rod, and detects the filling density of shredded tobacco, based on the degree of attenuation of the radial rays passing through the shredded tobacco.
The use of radial rays requires a strict control system as a safety measure, and it is not easy to handle the radial ray-type detecting device.
In view of this, filling density detecting devices using infrared rays in place of radial rays have been developed, and an example thereof is disclosed in Examined Japanese Patent Publication No. 8-2288. This known detecting device comprises a plurality of infrared light sources and a plurality of light receivers. The light sources and the light receivers are disposed along a horizontal delivery path for a tobacco rod in a cigarette manufacturing machine. The delivery path extends from a wrapping section of the cigarette manufacturing machine.
In the detecting device, infrared rays are irradiated from each light source toward the outer peripheral surface of tobacco rod, and the infrared rays which have been transmitted through the tobacco rod or diffused in gaps in the tobacco rod are received by each light receiver. Then, based on the quantity of the received infrared rays, a density signal indicative of the shredded tobacco filling density is output.
The output level of the density signal is higher in a diffusion type in which infrared rays are diffused than a transmission type in which infrared rays are transmitted, and a detecting device of the diffusion type is suitable for measuring the shredded tobacco filling density. Therefore, the filling density of the shredded tobacco in the tobacco rod may be measured by using the diffusion type detecting device, and in this case soft spots in the tobacco rod can also be detected. The soft spot here means a part of the tobacco rod having a shredded tobacco filling density lower than a reference range.
In the diffusion type detecting device (cf. FIG. 6) disclosed in the above publication, the infrared light sources and the light receivers are alternately disposed in the circumferential direction of the tobacco rod. Moreover, each light source and each light receiver are disposed so as to face another light source and another light receiver, respectively, across the tobacco rod.
For this reason, two opposed light sources irradiate only the same spot in the tobacco rod, so that the regions irradiated with infrared rays are narrow as viewed in the cross section of the tobacco rod. Accordingly, the known detecting device is low in diffusion efficiency of infrared rays in the tobacco rod, and thus is not capable of detecting the shredded tobacco filling density with high accuracy throughout the whole cross-sectional area of the tobacco rod.
Furthermore, since one pair of opposed light sources is disposed in a horizontal plane, the infrared rays incident from these light sources into the tobacco rod pass directly through the shredded tobacco, which is in a substantially vertically layered state, in the tobacco rod. Consequently, the known detecting device is not capable of satisfactorily diffusing infrared rays in the tobacco rod, showing low soft-spot detection accuracy.
An object of the present invention is to provide a detecting device capable of detecting with high accuracy a filling density of filler in a rod-shaped article by using inspection light except radial rays, which can be controlled easily.
The above object can be achieved by a detecting device of the present invention, comprising light incidence means for making inspection light incident into a rod-shaped article, light-receiving means for receiving the inspection light from the rod-shaped article, and measuring means for measuring a filling density of filler based on an output from the light-receiving means. The light incidence means has a plurality of light sources disposed in a predetermined arcuate area surrounding the rod-shaped article adjacently to each other in a circumferential direction of the rod-shaped article and causing the inspection light to enter the rod-shaped article in an identical cross section of the rod-shaped article. The light receiving means has at least one light receiver disposed in an area other than the arcuate area in the circumferential direction of the rod-shaped article so as not to face any of the light sources, receiving the inspection light emitted from the rod-shaped article along the cross section, and generating a signal indicative of the received-light quantity.
According to the above detecting device, the inspection light incident from each light source into the rod-shaped article is reflected by the filler in the rod-shaped article, and as the reflection is repeated, the inspection light is diffused in gaps in the rod-shaped article. Then, the diffused inspection light is emitted from the rod-shaped article and received by the light receiver. The light receiver supplies a signal corresponding to the quantity of the received inspection light to the measuring means, which measures the filling density of the filler based on the received signal.
Beams of the inspection light from the light sources enter the rod-shaped article in respective different directions, thereby irradiating a wide area of the rod-shaped article as viewed in the same cross section and diffusing uniformly throughout substantially the whole area of the cross section. As a result, the quantity of the diffused inspection light received by the light receiver represents an accurate density of the filler in the rod-shaped article.
The light incidence means may include four light sources arranged separately from one another at a predetermined angle in the circumferential direction of the rod-shaped article. The light receiving means may include two light receivers which are also arranged separately from each other at a predetermined angle in the circumferential direction of the rod-shaped article.
Where the rod-shaped article is a tobacco rod delivered in a horizontal direction from a wrapping section of a cigarette manufacturing machine, the detecting device measures a shredded tobacco filling density in the tobacco rod. In this case, it is preferable that each light source of the detecting device causes the inspection light to enter the tobacco rod in a direction other than the horizontal direction. As a consequence of such arrangement, the inspection light never passes through gaps of the shredded tobacco in the tobacco rod without being reflected, so that only the diffused inspection light is emitted from the tobacco rod.
More specifically, the four light sources are arranged separately from one another at an angle of 45xc2x0, while the two light receivers are arranged separately from each other at an angle of 90xc2x0. More preferably, two of the light sources are disposed adjacently to each other with a vertical longitudinal section of the rod-shaped article therebetween, and the remaining two light sources are disposed adjacently to each other with a horizontal longitudinal section of the rod-shaped article therebetween. With this arrangement, the inspection light from the light sources is diffused uniformly in the tobacco rod, which enables the light receivers to satisfactorily receive the inspection light emitted from the tobacco rod.
In this case, one of the light receivers may be disposed on the vertical longitudinal section, and the other may be disposed on the horizontal longitudinal section.
The light sources and the light receivers may be mounted on a holder surrounding the tobacco rod, and the light sources and the light receivers in this instance form one detecting unit.
Each light source is capable of making infrared rays as the inspection light incident into the tobacco rod. Infrared rays are excellent in diffusibility within the tobacco rod and can be easily controlled.